Knowledgebase
Garden Pests #664861
Asked July 16, 2020, 10:58 AM EDT
Otsego County Michigan
Expert Response
Hello,
Your trees have lichen on them. This is a harmless organism and doesn’t cause any damage. Lichen come in many colors and will change color depending on the moisture level or the season. Here is more information: https://www.canr.msu.edu/news/what_are_lichens_and_what_are_they_doing_on_my_tree
Your blacked-eyed susan may have fungal leaf spot, but the picture is a little out of focus, and I can’t see the details of the leaf well. Are the leaves getting wet when you water the plants or when you water a nearby lawn? This enables fungal diseases to develop. Here is information on the many fungal diseases that affect rudbeckia, and how to treat them-http://hyg.ipm.illinois.edu/pastpest/200507c.html
If the flowers are being kept dry by watering from below, then the damage may be from spider mites. Check the underside of the leaves for tiny mites and cast skins. Here are pictures and how to treat spider mites- https://extension.umd.edu/hgic/topics/spider-mites-flowers-and-groundcovers
I am not an expert in vegetables. Would you please submit your picture of the zucchini as a separate question, so it can be sent to a vegetable expert?
As far as the other plant - it has been suggested that the plant may have what is called leaf miner? I have no idea what that is. I have seen a particular spider on the the plant. I have sprayed with Neem Oil, however, it doesn't seem to be working.
I can’t see the damage clearly in your photos but yes, Rudbeckia hirta, black-eyed susan, is in the aster family of plants and there is a moth larva called aster leafminer.
I couldn’t find a reference showing it in Michigan, but it has been found in neighboring states. Here are pictures to compare with what you are seeing- http://entnemdept.ufl.edu/creatures/MISC/MOTHS/Leucospilapteryx_venustella.htm
There are other leafminers that feed on the aster family. So, you may have one of those. Chemical control typically has to be systemic or “translaminar” which means it can penetrate the leaf surface. Because the larvae feed in between the upper and lower layer of the leaf they are therefore protected by the leaf from contact insecticides like you used. This article lists chemicals for controlling leafminers in ornamental perennials- https://content.ces.ncsu.edu/columbine-leafminers-1
I hope this helps!
